1. Field of Invention
The present invention relates generally to the field of data networking and telecommunications. More particularly, in one exemplary aspect, the present invention is directed to the intelligent association of control symbols with special symbols that are transmitted over a network in order to improve DC-balance on a transmission medium.
2. Description of Related Technology
DisplayPort is an emerging digital display interface technology specified by the Video Electronics Standards Association (VESA). Current incarnations of the standard specify support for simple networking of digital audio/visual (A/V) interconnects, intended to be used primarily between an arbitrary assembly of multimedia “sources” (e.g., computers or CPUs) and “sinks” (e.g., display monitors, home-theater system, etc.). This interconnection is generally unidirectional in nature; i.e., from source to sink, in current implementations.
Extant DisplayPort technology is an extensible digital interface solution that is designed for a wide variety of performance requirements, and broadly supports PCs, monitors, panels, projectors, and high definition (HD) content applications. Current DisplayPort technology is also capable of supporting both internal (e.g., chip-to-chip), and external (e.g., box-to-box) digital display connections. Examples of internal chip-to-chip applications include notebook PCs, which drive a display panel from a graphics controller, or display components from display controllers driving the monitor of a TV. Examples of box-to-box applications include display connections between PCs and monitors, and projectors (e.g., not housed within the same physical device). Consolidation of internal and external signaling methods enables the “direct drive” of digital monitors. Direct drive eliminates the need for control circuits, and allows for among other things, cheaper and slimmer display devices.
The current revision of DisplayPort (DisplayPort1.1a) transmits both control symbols and data symbols. While data symbols are scrambled in order to, inter alia, provide DC-balance on the transmission medium, control symbols currently are not. Control symbols have historically not needed to be scrambled, as the transmission of non-scrambled control symbols allows the relatively rare control symbols to be instantly identified when received at, for example, a sink.
Revisions currently being considered for future revisions of DisplayPort have given rise to concerns of EMI and/or inter-symbol interference (ISI) over the transmission medium, as there are some circumstances in which certain control symbols may in the future occur at relatively closely spaced intervals, and/or repeat in a fashion which gives rise to interference concerns.
Accordingly, improved apparatus and methods are needed in order to address these future EMI and EMC concerns with regards to control symbols in a DisplayPort network. Such improved apparatus and methods would ideally reduce the effects of EMI in situations such as when the control symbols occur at closely spaced intervals. More generally, such apparatus and methods would provide for mechanisms that improve the characteristics of the symbols transmitted over the transmission medium, while advantageously leveraging existing hardware so as to minimize circuitry costs in future implementations.
In addition, such improved apparatus and methods would ideally take advantage of knowledge about the existing system including: (1) the expected frequency of transmitted control symbols; and (2) the EMI costs associated with expected control symbol transmission patterns; and/or (3) the specific control symbols that unambiguously identify major delineation points or functions in the format of the data.
Lastly, such improved apparatus and methods should not introduce significant costs in terms of communications bandwidth, in order to ensure that the system bandwidth is fully utilized whether or not control symbols are scrambled.